JP2001055935A - Variable valve timing controller for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the situation that feedback control before lock release disturbs the lock release, in a variable valve timing controller having a function for locking a cam shaft phase at a middle lock position positioned at a nearly middle point in a controllable range of the cam shaft phase during a stop of an internal combustion engine or when starting the engine. SOLUTION: In this controller, an unevenness degree RAN in an advance angle amount of a cam angle signal is calculated after a start, and lock release is decided when the unevenness degree RAN exceeds a prescribed value β. Then, feedback control of valve timing is started to feedback-control a hydraulic control valve such that an actual advance angle position coincides with a target advance angle position. Because the feedback control of the valve timing is started after detecting the lock release, the situation that the feedback control disturbs the lock release like before can be avoided, and the lock release is rapidly executed to shift to the feedback control.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable valve timing control for an internal combustion engine having a function of locking a camshaft phase at an intermediate lock position located substantially in the middle of an adjustable range when the internal combustion engine is stopped and started. It concerns the device.

[0002]

2. Description of the Related Art In recent years, an internal combustion engine mounted on a vehicle is increasingly employing a variable valve timing control device for the purpose of improving output, reducing fuel consumption and reducing exhaust emissions. For example, as shown in FIG. 20, a basic configuration of a vane type variable valve timing control device is connected to a housing 1 that rotates in synchronization with a crankshaft of an engine and a camshaft of an intake (or exhaust) valve. The fluid chamber 3 formed in the housing 1 is divided into an advance chamber 5 and a retard chamber 6 by a vane 4 provided in the rotor 2. Then, the hydraulic pressure in the advance chamber 5 and the retard chamber 6 is controlled by a hydraulic control valve to relatively rotate the housing 1 and the rotor 2 (vane 4), whereby the rotation phase of the camshaft with respect to the crankshaft (hereinafter referred to as “the camshaft”) The cam timing is varied to control the valve timing variably.

A conventional vane-type variable valve timing control apparatus has a camshaft phase most retarded when the engine is stopped (when the oil pressure is lowered) in order to prevent noise caused by vibration of the vane 4 at the time of starting. The relative rotation between the housing 1 and the rotor 2 (vane 4) is locked by the lock pin 7 in the retarded phase. Therefore, at the time of starting, since the engine is started with the most retarded phase, the most retarded phase is set to a phase suitable for starting.

However, in this configuration, since the most retarded phase is limited by the starting phase (lock position), the adjustable range of the valve timing (camshaft phase) is limited by the lock position, and the valve position is limited. There is a disadvantage that the adjustable range of timing is narrow.

Therefore, as disclosed in Japanese Patent Application Laid-Open No. Hei 9-324613, the valve timing (camshaft phase) is adjusted by setting the lock position when the engine is stopped at a substantially intermediate position in the adjustable range of the camshaft phase. It has been proposed to increase the possible range.

[0006]

The lock pin 7 for locking the camshaft phase is urged by a spring in the lock direction, and the lock is released by the advance chamber 5 and the retard chamber 6 with respect to the lock pin 7. Both hydraulic pressures act in the unlocking direction. When the engine is stopped, the oil pressure is reduced, so that the lock pin 7 is fitted into the lock hole by the spring force, and the camshaft phase is kept locked at the intermediate lock position. Therefore, when starting the engine, the engine is started with the camshaft phase locked at the intermediate lock position,
When the hydraulic pressure in the advance chamber 5 and the retard chamber 6 increases due to the increase in the hydraulic pressure accompanying the subsequent increase in the engine rotational speed (oil pump rotational speed), the lock pin 7 is pushed out of the lock hole by the hydraulic pressure, and the lock pin 7 is unlocked.
After the lock is released, the valve timing control is enabled, and the hydraulic control valve is feedback-controlled so that the actual valve timing (actual advance position) matches the target valve timing (target advance position).

[0007] However, the conventional configuration has a lock pin 7.
Since there is no function of detecting the lock release, feedback control is started before the lock release ends, and the hydraulic control valve is feedback controlled so that the actual advance position of the camshaft phase matches the target advance position. Usually, immediately after starting,
Although the target advance position is set near the intermediate lock position, the target advance position often moves away from the intermediate lock position over time. Therefore, if the lock release timing is delayed for some reason, the deviation between the actual advance position and the target advance position increases, and as a result, the advance chamber 5 and the retard chamber 6
The feedback control is performed such that one of the hydraulic pressures is increased and the other is decreased, resulting in an increase in the imbalance between the hydraulic pressures of the two chambers 5 and 6. In such an unbalanced oil pressure state, the lock pin 7 is strongly pressed from one side to the inner surface of the lock hole by hydraulic pressure, and the lock pin 7 is bitten into the lock hole, and the lock release time is increased. Is going to fall into a vicious circle that is increasingly delayed. As a result, there is a problem that the valve timing control is not performed normally, leading to a decrease in drivability, a decrease in fuel consumption, and a decrease in exhaust emission.

The present invention has been made in view of such circumstances, and a first object of the present invention is to prevent a situation in which the unlocking of the lock means is prevented by the feedback control before unlocking. In addition, a second object is to detect a lock failure or a lock release failure of the lock means at an early stage so that appropriate fail-safe measures can be taken.

[0009]

In order to achieve the first object, a variable valve timing control device according to a first aspect of the present invention comprises unlock detection means for detecting unlocking of the lock means. The feedback control of the valve timing is started after the lock release detecting means detects the lock release. With this configuration, since the feedback control is not performed until the lock is released, it is possible to avoid a situation in which the lock of the lock unit is prevented from being unlocked by the feedback control. And improve drivability, fuel efficiency, and exhaust emissions.

In this case, the presence or absence of unlocking of the locking means may be determined based on the degree of variation in the advance amount of the plurality of cam angle signals with respect to the crank angle signal. That is, if the variation in the advance amount of the plurality of cam angle signals is small, it is determined that the lock unit is in the locked state, and if the variation in the advance amount of the plurality of cam angle signals is large, it is determined that the lock is released. good. in this case,
Since the lock release can be detected using the crank angle signal and the cam angle signal used for discriminating the cylinder of the internal combustion engine and detecting the engine speed, it is possible to satisfy the demand for cost reduction without requiring a new sensor.

According to another aspect of the present invention, the cam angle detecting means outputs a cam angle signal for unlock detection at a different cam angle from the plurality of cam angle signals for cylinder discrimination. The configuration may be such that the presence / absence of unlocking of the locking means is determined from the magnitude of variation in the advance amount of a plurality of cam angle signals including the cam angle signal for detecting unlocking. Usually, the cam angle signal for cylinder discrimination is configured to be output at a cam angle at which the rotation of the cam shaft is relatively stable.
Although the variation of the advance angle of the cam angle signal is relatively small, unlock detection is performed at a different cam angle from the cam angle signal for cylinder discrimination (that is, a cam angle at which fine vibration of the cam shaft immediately after unlocking is easy to detect). Output the cam angle signal for
The variation in the amount of advance of the cam angle signal at the time of unlocking becomes large, so that it is easy to detect unlocking and the detection accuracy can be improved.

Further, as set forth in claims 4 and 15, the actual advance position of the camshaft phase is shifted from the intermediate lock position by a predetermined value (for example, the error factors such as the detection error of the actual advance position, manufacturing variations, and aging) are maximized. It may be determined that the locking means has been unlocked when the distance is equal to or greater than the limit value. Even in this case, unlocking can be detected with high accuracy, and
The need for cost reduction can be satisfied without requiring a new sensor.

Also, in consideration of the manufacturing variation in the intermediate lock position, the intermediate locking position may be set to the median (design median) of the manufacturing variation. As a result, the influence of manufacturing variations on the detection accuracy of unlocking can be reduced.

Alternatively, the intermediate lock position may be learned by the learning means while the locking means is locked. In this way, even if the manufacturing variation at the intermediate lock position is large, the unlocking can be detected with high accuracy without being affected by the manufacturing variation.

In order to achieve the second object of the present invention, the variation of the advance amount of a plurality of cam angle signals with respect to the crank angle signal and the actual advance of the cam shaft phase are set forth in claim 7. At least one of a lock failure and a lock release failure of the lock unit may be detected by the failure detection unit based on at least one of the angular positions. In this way, it is possible to detect a lock failure or a lock release failure without adding a new sensor, thereby satisfying the demand for cost reduction.

In this case, the cam angle detecting means can easily detect a cam angle different from a plurality of cam angle signals for cylinder discrimination (ie, a slight vibration of the cam shaft immediately after unlocking). (Cam angle) to output a cam angle signal for detecting a failure, and at least one of a lock failure and a lock release failure is determined based on the variation in the advance amount of a plurality of cam angle signals including the cam angle signal for failure detection. One may be determined. With this configuration, the variation in the amount of advance of the cam angle signal at the time of unlocking becomes large, so that it is easy to detect a lock failure or a lock release failure, and the detection accuracy can be improved.

Further, when the variation of the advance amounts of the plurality of cam angle signals is within a predetermined value in an area where the lock means needs to be in the unlocked state, it is determined that the lock is unsuccessful. You may do it. This makes it possible to accurately detect an unlock failure without adding a new sensor.

According to a tenth aspect of the present invention, when the variation of the advance amount of the plurality of cam angle signals is greater than a predetermined value in a region where the lock means needs to be in the locked state, it is determined that the lock is defective. May be. As a result, the lock failure can be accurately detected without adding a new sensor.

[0019] Further, as described in claim 11, a time period in which the actual advance position is within a predetermined value from the intermediate lock position while the target advance position is separated from the intermediate lock position by a predetermined value or more is set for a predetermined time. The lock release failure may be determined when the above is continued. Even in this case, the unlocking failure can be accurately detected without adding a new sensor.

Further, when the unlocking failure is detected, the unlocking failure return control means may apply hydraulic pressure to the locking means in the unlocking direction. With this configuration, when a lock release failure is detected, it is possible to quickly return to a normal lock release state, and it is possible to start feedback control of valve timing early.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Embodiment (1)] An embodiment (1) in which the present invention is applied to a variable valve timing control device for an intake valve will be described below with reference to FIGS. As shown in FIG. 1, in a DOHC engine 11 which is an internal combustion engine, power from a crankshaft 12 is transmitted to an intake side camshaft 16 and an exhaust side camshaft 17 by timing chains 13 via respective sprockets 14 and 15. It has become so. However, the intake camshaft 16 is provided with a valve timing adjusting device 18 for adjusting the advance amount of the intake camshaft 16 with respect to the crankshaft 12.

A cam angle sensor 19 (cam angle detecting means) is provided on the outer peripheral side of the intake camshaft 16.
A crank angle sensor 20 is provided on the outer peripheral side of the crankshaft 12.
(Crank angle detecting means) is provided. As shown in FIG. 9, the crank angle sensor 20 outputs a crank angle signal at every predetermined crank angle, and the engine speed is detected from the frequency of the crank angle signal. On the other hand, cam angle sensor 1
Numeral 9 outputs a cam angle signal at a plurality of cam angles for cylinder discrimination. FIG. 9 shows an example of a crank angle signal and a cam angle signal of a four-cylinder engine.
The output cam angle signal is output at every ° C.
° (180 ° C). That is, as shown in FIG. 8, four projections 72 a to 72 d are formed at 90 ° intervals on the outer periphery of the signal rotor 71 of the camshaft 16, and the cam angle sensor 19 faces the outer periphery of the signal rotor 71.
Are arranged, and the signal rotor 71 (the intake side camshaft 16) is provided.
Of the signal rotor 71, the projections 72a to 72a
Each time 2d faces the cam angle sensor 19, the cam angle sensor 1
9 outputs a pulse of the cam angle signal.

The output signals of the cam angle sensor 19 and the crank angle sensor 20 are input to an engine control circuit 21 which calculates the actual valve timing of the intake valve and outputs the output of the crank angle sensor 20. The engine speed is calculated from the pulse frequency. Further, output signals of various sensors (intake pressure sensor 22, water temperature sensor 23, throttle sensor 24, etc.) for detecting the engine operating state, and an ignition switch 25
The output signal of the timer 26 is also input to the engine control circuit 21.

The engine control circuit 21 performs fuel injection control and ignition control based on these various input signals, and also performs variable valve timing control, which will be described later, to determine the actual valve timing of the intake valve (for the intake camshaft 16). The valve timing adjustment device 18 is feedback-controlled so that the actual advance angle amount matches the target valve timing (target advance angle amount). The oil in the oil pan 27 is supplied to the oil pressure circuit of the valve timing adjusting device 18 via an oil pressure control valve 29 by an oil pump 28, and the oil pressure is controlled by the oil pressure control valve 29, whereby the intake camshaft is controlled. The 16 actual advance angle amounts (actual valve timings) are controlled.

Next, the structure of the valve timing adjusting device 18 will be described with reference to FIGS. The housing 31 of the valve timing adjusting device 18 is
Is fastened and fixed by bolts 32 to a sprocket 14 rotatably supported on the outer periphery of the sprocket. Thereby, the rotation of the crankshaft 12 is transmitted to the sprocket 14 and the housing 31 via the timing chain 13, and the sprocket 14 and the housing 31 rotate in synchronization with the crankshaft 12.

On the other hand, the intake camshaft 16 is rotatably supported by a cylinder head 33 and a bearing cap 34, and a rotor 35 is fixed to one end of the intake camshaft 16 by bolts 37 via stoppers 36. Have been. The rotor 35 is housed in the housing 31 so as to be relatively rotatable.

As shown in FIG. 3 and FIG.
A plurality of fluid chambers 40 are formed inside 1, and each fluid chamber 40 is partitioned into an advance chamber 42 and a retard chamber 43 by a vane 41 formed on the outer periphery of the rotor 35. And, on the outer peripheral portion of the rotor 35 and the outer peripheral portion of the vane 41,
Each of the seal members 44 is attached,
Are urged in the outer peripheral direction by a leaf spring 45 (see FIG. 2). Thereby, the gap between the outer peripheral surface of the rotor 35 and the inner peripheral surface of the housing 31 and the gap between the outer peripheral surface of the vane 41 and the inner peripheral surface of the fluid chamber 40 are sealed by the seal member 44.

As shown in FIG. 2, annular advance grooves 46 and retard grooves 47 formed on the outer peripheral portion of the intake camshaft 16 are connected to predetermined ports of the hydraulic control valve 29, respectively. When the oil pump 28 is driven by power, the oil pumped from the oil pan 27 is supplied to the advance groove 46 and the retard groove 47 via the hydraulic control valve 29. The advance oil passage 48 connected to the advance groove 46 is connected to the intake camshaft 1.
6 is formed so as to communicate with an arc-shaped advance oil passage 49 (see FIG. 3) formed on the left side surface of the rotor 35 through the interior of the rotor 6. Is in communication with On the other hand, the retard oil passage 50 connected to the retard groove 47 is
The arc-shaped retarded oil passage 51 is formed so as to penetrate through the inside of the intake-side camshaft 16 and communicate with an arc-shaped retarded oil passage 51 (see FIG. 4) formed on the right side surface of the rotor 35. It communicates with the retard chamber 43.

The hydraulic control valve 29 is a four-port, three-position switching valve that drives a valve body with a solenoid 53 and a spring 54. The valve body position is determined by a position for supplying hydraulic pressure to the advance chamber 42 and a retard chamber. The position is switched between a position where oil pressure is supplied to 43 and a position where oil pressure is not supplied to both the advance chamber 42 and the retard chamber 43. When the power supply to the solenoid 53 is stopped, the valve body is automatically switched to a position for supplying hydraulic pressure to the advance chamber 42 by the spring 54, and hydraulic pressure acts in a direction for advancing the camshaft phase.

In a state where a hydraulic pressure equal to or more than a predetermined pressure is supplied to the advance chamber 42 and the retard chamber 43, the vane 41 is fixed by the hydraulic pressure of the advance chamber 42 and the retard chamber 43, and the rotation of the crankshaft 12 The rotation of the housing 31 causes the rotation of the rotor 35 via oil.
(The vane 41), and the intake-side camshaft 16 is rotationally driven integrally with the rotor 35. During operation of the engine, the hydraulic pressure in the advance chamber 42 and the retard chamber 43 is controlled by the hydraulic control valve 29 to relatively rotate the housing 31 and the rotor 35 (vane 41), so that the intake-side cam with respect to the crankshaft 12. The rotation timing of the shaft 16 (hereinafter referred to as “camshaft phase”) is controlled to vary the valve timing of the intake valve. The sprocket 14 accommodates a torsion coil spring 55 (see FIG. 2) that assists the hydraulic pressure for relatively rotating the rotor 35 in the advance direction during the advance control by a spring force.

As shown in FIGS. 3 and 4, stopper portions 56 are formed on both sides of one of the vanes 41 to regulate the relative rotation range of the rotor 35 (vane 41) with respect to the housing 31. The stopper portion 56 regulates the most retarded phase and the most advanced phase of the camshaft phase. Further, the lock pin receiving hole 57 formed in the other vane 41 has the housing 31 and the rotor 35 (the vane 4).
Lock pin 58 for locking relative rotation with 1)
(Lock means) is accommodated, and the lock pin 58 is fitted into a lock hole 59 (see FIG. 2) provided in the housing 31, so that the camshaft phase is substantially at an intermediate position (intermediate lock position) of its adjustable range. Locked by. This intermediate lock position is set to a phase suitable for starting.

As shown in FIGS. 6 and 7, the lock pin 5
8 is slidably inserted into a cylindrical member 61 fitted on the inner periphery of the lock pin receiving hole 57, and is urged by a spring 62 in the lock direction (projection direction). Further, a gap between the cylindrical member 61 and the lock pin 58 is partitioned into a lock hydraulic chamber 64 and a lock release hydraulic chamber 65 by a valve portion 63 formed at a central outer peripheral portion of the lock pin 58. In order to supply hydraulic pressure from the advance chamber 42 to the lock hydraulic chamber 64 and the lock release hold hydraulic chamber 65, the vane 41 has a lock oil passage 66 communicating with the advance chamber 42 and a lock release hold An oil passage 67 is formed.
The housing 31 has a lock hole 59 and a retard chamber 43.
And a lock release oil passage 68 is formed.

As shown in FIG. 6, when the lock pin 58 is locked, the valve portion 63 of the lock pin 58 closes the oil passage 67 for holding and releasing the lock, and the lock oil passage 66 communicates with the lock hydraulic chamber 64. State. Thereby, the advance chamber 42
The lock hydraulic chamber 64 is supplied with a hydraulic pressure, and the lock pin 58 is held in the lock hole 59 by the hydraulic pressure and the spring 62 so that the camshaft phase is locked at the intermediate lock position.

While the engine is stopped, the hydraulic pressure in the lock hydraulic chamber 64 (the hydraulic pressure in the advance chamber 42) decreases.
As a result, the lock pin 58 is held at the lock position. Therefore, the engine is started in a state where the lock pin 58 is held at the lock position (intermediate lock position). When the oil pressure in the lock hole 59 (the oil pressure in the retard chamber 43) increases after the engine starts, the engine starts to operate. The lock of the lock pin 58 is released as follows. After the engine is started, the hydraulic pressure (force in the unlocking direction) supplied from the retard chamber 43 to the lock hole 59 through the unlocking oil passage 68 changes the hydraulic pressure of the lock hydraulic chamber 64 (the hydraulic pressure of the advance chamber 42) and the hydraulic pressure of the spring 62. When the combined force with the spring force (force in the locking direction) becomes larger, the lock pin 58 is pushed out of the lock hole 59 by the hydraulic pressure of the lock hole 59 and moves to the unlock position shown in FIG. Is done.

In this unlocked state, as shown in FIG. 7, the valve portion 63 of the lock pin 58 closes the lock oil passage 66, and the lock release holding oil passage 67 is connected to the lock release holding hydraulic chamber 65. It will be in the state of communication. Accordingly, the hydraulic pressure is supplied from the advance chamber 42 to the hydraulic chamber 65 for holding and releasing the lock, and the hydraulic pressure of the hydraulic chamber 65 for holding and releasing the lock (the hydraulic pressure of the advance chamber 42) and the hydraulic pressure of the lock hole 59 (the retard angle). The lock pin 58 is held at the unlocked position against the spring 62 by the pressure of the chamber 43).

During operation of the engine, the advance chamber 42 and the retard chamber 4
3, the lock pin 58 is held at the unlocked position by the hydraulic pressure, and the housing 31 and the rotor 35 can be relatively rotated (that is, the valve timing can be controlled). Is held.

During operation of the engine, the engine control circuit 21
Is the actual valve timing VT of the intake valve based on the output signals of the crank angle sensor 20 and the cam angle sensor 19.
(The actual advance position of the intake camshaft 16), and
The target valve timing VTT of the intake valve (the target advance position of the intake camshaft 17) is calculated based on the outputs of various sensors that detect the operating state of the engine, such as the intake pressure sensor 22 and the water temperature sensor 23. Then, the hydraulic control valve 29 of the valve timing adjusting device 18 is feedback-controlled so that the actual valve timing VT of the intake valve matches the target valve timing VTT. Thereby, the advance chamber 4
By controlling the hydraulic pressure of the second and retard chambers 43 to relatively rotate the housing 31 and the rotor 35, the camshaft phase is changed to make the actual valve timing VT of the intake valve coincide with the target valve timing VTT.

Thereafter, when the engine 11 is stopped,
When the engine speed decreases, the discharge pressure of the oil pump 28 decreases, so that the hydraulic pressure of the advance chamber 42 and the retard chamber 43 decreases. As a result, the hydraulic chamber 6 for unlocking and holding
5 (oil pressure in the advance chamber 42) and the oil pressure in the lock hole 59 (oil pressure in the retard chamber 43) decrease, and the spring force of the spring 62 overcomes these oil pressures. As a result, the lock pin 58 projects and fits into the lock hole 59. However, lock pin 5
In order for 8 to fit into the lock hole 59, the two positions must match, that is, the camshaft phase must match the intermediate lock position.

When the engine 11 stops, the engine rotation speed (the rotation speed of the oil pump 28) decreases and the oil pressure decreases, so that the camshaft phase naturally shifts to the retard side due to the load torque of the camshaft 16. In the process, as shown in FIG. 6, the lock pin 58 is fitted into the lock hole 59 to lock the camshaft phase at the intermediate lock position.

As described above, the engine is started in a state where the lock pin 58 is held at the lock position (intermediate lock position). After the engine is started, the oil pressure in the lock hole 59 (the oil pressure in the retard chamber 43) is increased. When the pressure rises, the lock of the lock pin 58 is released by the hydraulic pressure, and by this release of the lock, feedback control of the valve timing (camshaft phase) becomes possible.

However, in the conventional structure, the lock pin 5
Since there is no function to detect the unlocking of the lock 8, the feedback control is started before the unlocking is completed, and the hydraulic control valve 29 is feedback-controlled so that the actual advanced position of the camshaft phase matches the target advanced position. I do. Normally, immediately after starting, the target advance position is set near the intermediate lock position, but in many cases, the target advance position moves away from the intermediate lock position over time. Accordingly, if the lock release timing is delayed for some reason, the deviation between the actual advance position and the target advance position increases, and as a result, the difference between the hydraulic pressures of the advance chamber 42 and the retard chamber 43 increases. In this case, feedback control is performed in the direction in which the lock is released, and the timing of unlocking is further delayed, resulting in a vicious cycle. As a result, there is a problem that the valve timing control is not performed normally, leading to a decrease in drivability, a decrease in fuel consumption, and a decrease in exhaust emission.

Therefore, in this embodiment (1), the presence or absence of unlocking of the lock pin 58 is determined by the unlock detection program of FIG. 10, and the feedback control is started after the unlock detection by the valve timing control program of FIG. I do. These programs are stored in a ROM (storage medium) built in the engine control circuit 21 and executed by the microcomputer of the engine control circuit 21. Hereinafter, the processing contents of these programs will be described.

The unlock detection program shown in FIG. 10 is executed periodically and repeatedly, and plays a role as unlock detection means referred to in the claims. When this program is started, first, in step 101, it is determined whether or not the current actual advance position (actual valve timing) VT is within a predetermined range (VTA <VT <VTB) near the intermediate lock position. Here, the predetermined range (VTA <VT <VTB) is
The range is set within a predetermined value (for example, a value in which an error factor such as a detection error of the actual advance position VT, a manufacturing variation, and a change with time) is maximally estimated from the intermediate lock position. The intermediate lock position used as the median of this predetermined range is set to the median of manufacturing variations (design median).

If the current actual advance position VT is not within the predetermined range near the intermediate lock position, the camshaft phase is far from the intermediate lock position even if error factors such as a detection error are considered to the utmost. It is clear that step 105
Then, it is determined that the lock of the lock pin 58 is released, and the program is terminated.

On the other hand, if the current actual advance position VT is within the predetermined range near the intermediate lock position, the routine proceeds to step 102, where the present actual advance position VT (i) and the previous actual advance position VT
It is determined whether the operating state is stable based on whether the deviation from (i-1) is smaller than a predetermined value α. In a region where the operating state is not stable, the detection variation of the actual advance position VT (i) tends to be large, and the following steps 103 to 103 will be described later.
This is because, in the detection method of 106, the detection accuracy of unlocking is deteriorated. Therefore, when the deviation between the current actual advance position VT (i) and the previous actual advance position VT (i-1) is equal to or larger than the predetermined value α, the state where the lock release cannot be accurately detected is determined. Judgment is made and this program is ended without performing the subsequent processing.

On the other hand, if the deviation between the current actual advance position VT (i) and the previous actual advance position VT (i-1) is smaller than a predetermined value α, it is determined that the unlocking can be detected. Judge,
Proceeding to step 103, the variation degree RAN of the advance amounts of the plurality of cam angle signals is calculated by one of the following two methods.

[First Calculation Method] As shown in FIG.
Advance amounts VT [1], VT [2], VT [3] of the cam angle signals
, VT [4], RAN [1], RAN [2], R
AN [3] and RAN [4] are calculated by the following equations. RAN [1] = VT [1] -VT [4] RAN [2] = VT [2] -VT [1] RAN [3] = VT [3] -VT [2] RAN [4] = VT [4] -VT [3] and these four deviations RAN [1], RAN [2], R
AN [3] and RAN [4] are integrated to determine the degree of variation RAN in the advance amount of the cam angle signal. RAN = | RAN [1] + RAN [2] + RAN [3] + RA
N [4] |

[Second Calculation Method] The advance amounts VT [1], VT [2], VT [3], and VT [1] of the four cam angle signals output from the cam angle sensor 19 in one rotation of the cam shaft 16. The deviation RAN [1], RAN [2], RA of each of the current value and the previous value of VT [4]
N [3] and RAN [4] are calculated. RAN [1] = VT [1] (i) -VT [1] (i-1) RAN [2] = VT [2] (i) -VT [2] (i-1) RAN [3] = VT [3] (i) -VT [3] (i-1) RAN [4] = VT [4] (i) -VT [4] (i-1) And these four deviations RAN [1], RAN [2], R
AN [3] and RAN [4] are integrated to determine the degree of variation RAN in the advance amount of the cam angle signal. RAN = | RAN [1] + RAN [2] + RAN [3] + RA
N [4] |

After calculating the degree of variation RAN by any of the methods described above, the routine proceeds to step 104, where the degree of variation RAN of the advance amount of the cam angle signal is compared with a predetermined value β, and the degree of variation RAN is determined by the predetermined value β. If it is below, it is considered that the camshaft phase is fixed at the intermediate lock position and does not move at all, so the process proceeds to step 106, it is determined that the lock pin 58 is locked, and the unlock detection flag is turned off. Keep in state.

On the other hand, if the degree of variation RAN of the amount of advance of the cam angle signal is larger than the predetermined value β, it is considered that the camshaft phase is slightly vibrating near the intermediate lock position. Proceed to 105 and lock pin 58
Is determined to be unlocked, and the unlock detection flag is turned ON. In other words, when the lock of the lock pin 58 is released, the camshaft phase slightly vibrates even if the camshaft phase is controlled near the intermediate lock position by hydraulic pressure. The degree of variation RAN of the advance amount of the cam angle signal is exploited by utilizing the characteristic that
It is also possible to determine the presence / absence of unlocking based on the size of.

Incidentally, the degree of variation R of the advance angle of the cam angle signal
The method of obtaining AN is based on the advance angle deviation RAN of each cam angle signal.
In addition to the method of integrating [1] to RAN [4], for example, the difference between the maximum value and the minimum value of the cam angle signal advance angle deviation is used as the variation degree RAN, or the maximum value is used as the variation degree RAN. In short, the point is that the degree of variation of the amount of advance of the cam angle signal expressed by a numerical value may be used as the degree of variation RAN.

Next, the processing contents of the valve timing control program of FIG. 11 will be described. This program is executed periodically and repeatedly, and plays a role as a valve timing control means referred to in the claims. When the program is started, first, in step 111, it is determined whether or not the lock release of the lock pin 58 is detected by the lock release detection program of FIG. 10 (whether or not the lock release detection flag is ON). If the lock release has not been detected yet, the process proceeds to step 112, and it is determined whether or not the lock release execution condition is satisfied. Here, the unlocking execution condition is, for example, that a predetermined time has elapsed from the start, or that the oil pressure discharged from the oil pump 28 has risen to a predetermined value or more.

If the lock release execution condition is not satisfied, the program is immediately terminated. If the lock release execution condition is satisfied, the process proceeds to step 113, and
The lock release control is executed to release the lock of the lock pin 58. In this unlocking control, hydraulic pressure is supplied to the retard chamber 43, and the hydraulic pressure is supplied from the retard chamber 43 to the unlocking oil passage 68.
The lock pin 58 is pushed out of the lock hole 59 by this hydraulic pressure, and the lock of the lock pin 58 is released.

On the other hand, in step 111, the lock pin 58
If it is determined that the lock release of
In step 14, feedback control of valve timing is started, and the hydraulic control valve 29 is feedback-controlled so that the actual advance position (actual valve timing) VT coincides with the target advance position (target valve timing) VTT. The hydraulic pressures in the chamber 42 and the retard chamber 43 are controlled.

The control example of the embodiment (1) described above will be described with reference to the time chart of FIG. When the lock pin 58 is unlocked due to an increase in the oil pressure accompanying an increase in the engine speed (oil pump speed) after the start, the degree of variation RAN in the amount of advance of the cam angle signal gradually increases. When the degree of variation RAN exceeds the predetermined value β, it is determined that the lock is released, and the lock release detection flag is turned ON. As a result, feedback control of the valve timing is started, and the hydraulic control valve 29 is feedback-controlled so that the actual advance position (actual valve timing) VT matches the target advance position (target valve timing) VTT.

In this case, the feedback control of the valve timing is started after detecting the unlocking of the lock pin 58, so that the feedback control is not started until the unlocking ends. For this reason, it is possible to avoid a situation in which the lock release of the lock pin 58 is hindered by the feedback control as in the related art, and it is possible to quickly release the lock and shift to the feedback control, thereby improving drivability, fuel consumption, and exhaust emission. It can be improved than before.

Moreover, in this embodiment (1), unlocking is detected based on the degree of variation RAN of the advance amount of the cam angle signal, so that it is not necessary to add a new sensor for unlocking detection, and low The requirement for cost reduction can be satisfied.

[Embodiment (2)] By the way, as the variation RAN of the advance amount of the cam angle signal caused by the slight vibration of the cam shaft 16 immediately after the lock pin 58 is unlocked becomes larger, the variation RAN before and after the lock is released is increased. Greatly appears, the detection of unlocking becomes easy, and the detection accuracy can be improved.

Normally, the cylinder angle cam angle signal is output at a cam angle at which the rotation of the cam shaft 16 is relatively stable so that stable cylinder identification can be performed.
The variation in the amount of advance of the cam angle signal is relatively small. Accordingly, there is a possibility that the difference in the degree of variation RAN of the advance angle of the cam angle signal before and after the lock pin 58 is unlocked does not appear so large.

Therefore, in the embodiment (2) of the present invention, as shown in FIG. 13, four protrusions 72a to 72c for cylinder discrimination on the outer periphery of the signal rotor 71 of the intake camshaft 16 are provided.
A protrusion 72e for unlock detection is formed at a position different from 2d, and as shown in FIG. 14, a cam angle (VT) different from the cam angle signals VT [1] to VT [4] for cylinder discrimination. That is, a cam angle signal VT [5] for unlock detection is output at a cam angle at which the minute vibration of the intake camshaft 16 immediately after unlocking is easily detected. In this case as well, the lock release is detected by the above-described lock release detection program in FIG. 10, and at this time, in step 103, the degree of variation RAN of the advance amounts of the plurality of cam angle signals is calculated by the following method.

First, with reference to the advance amount VT [5] of the cam angle signal for unlock detection, the amount of advance between the advance amounts VT [1] to VT [4] of the other four cam angle signals is determined. Deviation RAN [1], RAN
[2], RAN [3] and RAN [4] are calculated by the following equations.

RAN [1] = VT [1] -VT [5] RAN [2] = VT [2] -VT [5] RAN [3] = VT [3] -VT [5] RAN [4] = VT [4] -VT [5]

Then, these four deviations RAN [1] to R
AN [4] is integrated to determine the degree of variation RAN in the advance amount of the cam angle signal. The advance angle deviation VT [k] of the cam angle signal
Calculates the mutual deviation RAN [k] of the advance amounts VT [1] to VT [5] of the five cam angle signals using the first calculation method described in the embodiment (1). The advance amount VT of the five cam angle signals may be calculated using the second calculation method.
The deviation RAN between the current value and the previous value of each of [1] to VT [5]
[k] may be calculated. The processing of the other steps is the same as that of the embodiment (1).

As in the present embodiment (2), a cam angle different from the cam angle signals VT [1] to VT [4] for discriminating the cylinders (ie, a slight vibration of the intake camshaft 16 immediately after the lock is released). Cam angle signal VT for unlock detection
[5], the degree of variation RAN in the amount of advance of the cam angle signal before and after the lock is released greatly differs, so that the detection of the lock release is facilitated and the detection accuracy can be improved.

It should be noted that the cam angle signal for unlock detection may be output at two or more locations. Needless to say, the cam angle signal for cylinder determination is not limited to four.

[Embodiment (3)] In the embodiment (1), step 10 of the unlock detection program shown in FIG.
Although the median value (intermediate lock position) of the predetermined range (VTA <VT <VTB) used in 1 is set to the median value (design median value) of manufacturing variation, in the embodiment (3) of the present invention shown in FIG. The intermediate lock position is learned while the lock pin 58 is locked, and the learning value of the intermediate lock position is used to determine the predetermined range (VTA <VT <VT) used in step 101.
B) is set.

The unlock detection program of FIG. 15 executed in this embodiment (3) is obtained by adding the processing of steps 100 and 107 to the program of FIG. 10, and the processing of the other steps is the same as that of FIG. It is the same as the program.

In the unlock detection program shown in FIG.
When it is determined in step 106 that the lock pin 58 is locked, the process proceeds to step 107, in which the actual advance angle position (actual valve timing) VTO at that time is learned as an intermediate lock position, and a non-volatile memory such as a backup RAM is used. To memorize it. The processing of step 107 plays a role corresponding to the learning means in the claims.

Next, when this program is started next time, at step 100, the learning value VTO of the intermediate lock position is obtained.
Is read from the memory, and the learning value VTO is set to a predetermined value δ.
Are added and subtracted to obtain boundary values VTA and VTB in a predetermined range. VTA = VTO−δ VTB = VTO + δ Here, the predetermined value δ is set to a value that takes into account error factors such as a detection error of the actual advance angle position VT, manufacturing variations, and aging.

As described above, the predetermined range (VTA <VT <) calculated based on the learned value VTO of the intermediate lock position is obtained.
In the next step 101, it is determined whether or not the current actual advance position VT is within a predetermined range, and if it is not within the predetermined range, error factors such as a detection error are considered as much as possible. However, since it is clear that the camshaft phase is far from the intermediate lock position, the process proceeds to step 105, where it is determined that the lock of the lock pin 58 is released.

In the above-described embodiment (3), since the intermediate lock position is learned, the lock release can be accurately detected without being affected by manufacturing variations, aging, and the like.

[Embodiment (4)] The embodiment (4) of the present invention shown in FIGS. 16 and 17 has a function of detecting a lock release failure and a function of executing lock release control when the lock release failure is detected. ing.

The unlocking failure detecting program shown in FIG. 16 is periodically and repeatedly executed, and plays a role as a failure detecting means referred to in the claims. When the program is started, first, in step 201, it is determined whether or not the lock release control has been completed. If the lock release control has not been completed, it is considered that the lock pin 58 is still in the locked state. This program ends without performing the subsequent unlocking failure detection processing.

Thereafter, when the lock release control ends, the routine proceeds to step 202, where the current actual advance position VT is within a predetermined range near the intermediate lock position (VTA <VT <VT).
B) is determined. The method of setting the predetermined range may be the same method as in the embodiment (1) or (3).
If the current actual advance position VT is not within the predetermined range near the intermediate lock position, it is determined that lock release has been performed normally (step 205).

On the other hand, if the current actual advance position VT is within the predetermined range near the intermediate lock position, the process proceeds to step 203, and the degree of variation RAN of the advance amount of the cam angle signal is determined in the embodiment (1) or (2). It is calculated by the same method as in 2). Thereafter, the routine proceeds to step 204, where the variation degree RAN of the advance angle amount of the cam angle signal is compared with a predetermined value β, and the variation degree RA
If N is equal to or smaller than the predetermined value β, it is considered that the camshaft phase is fixed at the intermediate lock position and does not move at all, so the process proceeds to step 206, and it is determined that the lock release is defective. On the other hand, the degree of variation RA of the advance amount of the cam angle signal RA
If N is larger than the predetermined value β, it is considered that the camshaft phase is slightly vibrating in the vicinity of the intermediate lock position. Therefore, the process proceeds to step 205, where it is determined that the lock has been normally released.

The unlocking failure recovery control program shown in FIG. 17 is periodically and repeatedly executed, and functions as an unlocking failure recovery control means described in the claims.
When this program is started, first in step 301,
It is determined whether or not a lock release failure is detected by the lock release failure detection program in FIG. 16. If the lock release failure is not detected, the program is terminated as it is. If the lock release failure is detected, Step 3
02, the lock release control is executed, and the lock pin 58
Unlock.

In the embodiment (4) described above, FIG.
Since the unlocking failure detection program detects the unlocking failure based on the variation degree RAN of the advance angle of the cam angle signal, the unlocking failure detection can be performed without adding a new sensor. To meet the demand for cost reduction. In addition, the lock release control is executed when a lock release failure is detected,
The unlocking failure can be promptly returned to the normal unlocked state, and the feedback control of the valve timing can be started early.

[Embodiment (5)] In the embodiment (5) of the present invention, an unlock failure is detected by the unlock failure detection program of FIG. 18 as follows. First,
In step 401, it is determined whether or not the lock release control has been completed. If the lock release control has not been completed, it is considered that the lock pin 58 is still in the locked state. Exit this program without performing.

Thereafter, when the lock release control ends, the routine proceeds to step 202, where the current target advance position VTT is set.
Is within a predetermined range near the intermediate lock position (VTA <VTT <
VTB). The method of setting the predetermined range may be the same method as in the embodiment (1) or (3). If the current target advance position VTT is within a predetermined range near the intermediate lock position, the present program is terminated without performing the subsequent unlock failure detection processing.

On the other hand, if the current target advance angle position VTT is not within the predetermined range near the intermediate lock position, step 403
To determine whether or not the current actual advance position VT is within a predetermined range near the intermediate lock position (VTA <VT <VTB). This predetermined range may be the same as the predetermined range used in step 402. If the current actual advance position VT is not within the predetermined range near the intermediate lock position, it is determined that lock release has been normally performed (step 407).

If the current actual advance position VT is within a predetermined range near the intermediate lock position, the routine proceeds to step 404, where the time counter C is counted up, and the target advance position VTT is set to a predetermined value near the intermediate lock position. The time C in which the state where the actual advance position VT is within the predetermined range near the intermediate lock position despite the fact that it is not within the range continues is counted. Then, in the next step 405, it is determined whether or not the time C has exceeded a predetermined time T. Here, the predetermined time T
Is set to a time necessary and sufficient to control the actual advance position VT near the target advance position VTT. Therefore, if it is determined “Yes” in step 405, that is, even if the predetermined time T is exceeded, the actual advance position VT is changed to the target advance position VTT.
If the control cannot be performed in the vicinity, it is considered that the camshaft phase is fixed at the intermediate lock position and does not move at all. Therefore, the process proceeds to step 406, and it is determined that the lock release is defective.

In the unlocking failure method of the embodiment (5) described above, similarly to the embodiment (4), the unlocking failure can be detected without adding a new sensor, and the cost can be reduced. Requirements can be met.

[Embodiment (6)] In the embodiment (6) of the present invention, a lock failure is detected by the lock failure detection program of FIG. 19 as follows. First, in step 501, it is determined whether or not the lock release control has been performed. If the lock release control has already been performed, the program is terminated without performing the subsequent lock failure detection processing.

On the other hand, if the lock release control has not yet been performed, the routine proceeds to step 502, where it is determined whether or not the current actual advance position VT is within a predetermined range near the intermediate lock position (VTA <VT <VTB). The method of setting the predetermined range may be the same method as in the embodiment (1) or (3). If the current actual advance position VT is not within the predetermined range near the intermediate lock position, it can be determined that the camshaft phase is distant from the intermediate lock position.

If the current actual advance position VT is within a predetermined range near the intermediate lock position, the process proceeds to step 503, and the variation degree RAN of the advance amount of the cam angle signal is determined by using the embodiment (1) or (2). It is calculated by the same method as in 2). Thereafter, the process proceeds to step 504, where the variation degree RAN of the advance angle amount of the cam angle signal is compared with a predetermined value β, and the variation degree RA
If N is equal to or less than the predetermined value β, it is considered that the camshaft phase is fixed at the intermediate lock position and does not move at all, so the process proceeds to step 505 to determine that the lock state is normal. On the other hand, the degree of variation R of the advance amount of the cam angle signal R
If AN is larger than the predetermined value β, it is considered that the camshaft phase is slightly vibrating in the vicinity of the intermediate lock position, so the process proceeds to step 506, and it is determined that the lock is poor.

In the embodiment (6) described above, a lock failure can be detected without adding a new sensor, and the demand for cost reduction can be satisfied. still,
The above embodiments (1) to (6) may be implemented in combination as appropriate.

In each of the embodiments (1) to (6),
Although the present invention is applied to a variable valve timing control device for an intake valve, the present invention may be applied to a variable valve timing control device for an exhaust valve. In addition, in the present invention, the structure of the valve timing adjusting device may be changed as appropriate. In short, the valve timing adjusting device may be any type that locks the camshaft phase at the intermediate lock phase.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an entire control system showing an embodiment (1) of the present invention.

FIG. 2 is a longitudinal sectional view of a valve timing adjusting device.

FIG. 3 is a sectional view taken along the line AA of FIG. 2;

FIG. 4 is a sectional view taken along line BB in FIG. 2;

FIG. 5 is a sectional view taken along the line CC of FIG. 4;

FIG. 6 is a partially enlarged sectional view showing a locked state of a lock pin.

FIG. 7 is a partially enlarged cross-sectional view showing an unlocked state of a lock pin.

FIG. 8 is a diagram illustrating the structure of a cam angle sensor.

FIG. 9 is a time chart illustrating a relationship between a cam angle signal and a crank angle signal according to the embodiment (1).

FIG. 10 is a flowchart showing the flow of processing of an unlock detection program according to the embodiment (1).

FIG. 11 is a flowchart showing the flow of processing of a valve timing control program according to the embodiment (1).

FIG. 12 is a time chart showing a control example of the embodiment (1).

FIG. 13 is a view for explaining the structure of a cam angle sensor according to the embodiment (2).

FIG. 14 is a time chart illustrating a relationship between a cam angle signal and a crank angle signal according to the embodiment (2).

FIG. 15 is a flowchart showing the flow of processing of an unlock detection program according to the embodiment (3).

FIG. 16 is a flowchart showing a processing flow of an unlock failure detection program according to the embodiment (4).

FIG. 17 is a flowchart showing the flow of processing of an unlock failure recovery control program according to the embodiment (4).

FIG. 18 is a flowchart showing the flow of processing of an unlock failure detection program according to the embodiment (5).

FIG. 19 is a flowchart showing the processing flow of a lock failure detection program according to the embodiment (6).

FIG. 20 is a sectional view of a conventional valve timing adjusting device.

[Explanation of symbols]

11 ... engine (internal combustion engine), 12 ... crankshaft, 13
... Timing chains, 14, 15 ... Sprockets, 1
6 ... intake cam shaft, 17 ... exhaust cam shaft, 18 ... valve timing adjustment device, 19 ... cam angle sensor (cam angle detection means), 20 ... crank angle sensor (crank angle detection means), 21 ... engine control circuit (lock) Release detection means,
Valve timing control means, failure detection means, unlock release control means, learning means, actual advance position calculation means), 28
... oil pump, 29 ... hydraulic control valve, 31 ... housing, 35 ... rotor, 40 ... fluid chamber, 41 ... vane, 42
... advance chamber, 43 ... retard chamber, 53 ... solenoid, 54 ... spring, 58 ... lock pin (lock means), 59 ... lock hole.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Osamu Sato 1-1-1, Showa-cho, Kariya-shi, Aichi F-term in DENSO Corporation (reference) 3G016 AA08 AA19 BA23 BA38 CA04 CA13 CA21 CA24 CA27 CA33 CA36 CA48 CA51 CA59 DA06 DA22 GA07 3G084 BA23 CA01 CA07 DA27 EA07 EA11 EB12 EB22 FA00 FA10 FA11 FA20 FA35 FA36 FA38 FA39 3G092 AA11 DA01 DA09 DF04 DF09 DG02 DG05 EA12 EA13 EA15 EA17 EC03 EC05 FA03 FA09 FA15 FA05 FA50 FA13 FA05 FA05 FA05 HE01Z HE03Z HE05Z HE08Z

Claims (15)

[Claims] 1. A valve timing control means for variably controlling a valve timing by changing a rotation phase of a camshaft with respect to a crankshaft of an internal combustion engine (hereinafter, referred to as a "camshaft phase") by hydraulic pressure, while the internal combustion engine is stopped and started. Locking means biased to lock the camshaft phase at an intermediate locking position located approximately in the middle of the adjustable range of the camshaft phase. Wherein the valve timing control means starts feedback control of the valve timing after detecting the lock release of the lock means by the lock release detection means. Variable valve timing control device. 2. The system according to claim 1, further comprising: crank angle detection means for outputting a crank angle signal for each predetermined crank angle; and cam angle detection means for outputting a cam angle signal at a plurality of cam angles for cylinder discrimination. 2. The variable internal combustion engine according to claim 1, wherein the detection unit determines whether or not the lock unit is unlocked based on a variation in the advance amount of the plurality of cam angle signals with respect to the crank angle signal. 3. Valve timing control device. 3. The lock angle detection means outputs a lock angle detection cam angle signal at a different cam angle from the plurality of cam angle signals for cylinder discrimination. 3. The variable valve according to claim 2, wherein whether or not the lock means is unlocked is determined based on the degree of variation in the advance amount of the plurality of cam angle signals including the cam angle signal for detecting the release. Timing control device. 4. The lock release detecting means determines that the lock means has been released when the actual advance position of the camshaft phase is separated from the intermediate lock position by a predetermined value or more. Item 4. The variable valve timing control device for an internal combustion engine according to any one of Items 1 to 3. 5. The variable valve timing control device for an internal combustion engine according to claim 4, wherein the intermediate lock position is set to a median value of manufacturing variation. 6. The variable valve timing control device for an internal combustion engine according to claim 4, further comprising a learning unit that learns the intermediate lock position while the locking unit is locked. 7. A valve timing control means for variably controlling a valve timing by changing a rotation phase of a camshaft with respect to a crankshaft of an internal combustion engine (hereinafter, referred to as a "camshaft phase") by hydraulic pressure, while the internal combustion engine is stopped and started. Locking means biased to lock the camshaft phase at an intermediate locking position located approximately at the center of the adjustable range, crank angle detecting means for outputting a crank angle signal for each predetermined crank angle, Cam angle detection means for outputting a cam angle signal at a plurality of cam angles for cylinder discrimination, and an actual advance angle for calculating an actual advance position of the camshaft phase based on the crank angle signal and the cam angle signal A variable valve timing control device for an internal combustion engine, comprising: a position calculating means; Variable valve timing control apparatus for an internal combustion engine, characterized in that on the basis of at least one of the actual advance position of the phase and a failure detection means for detecting at least one of the lock failure and unlocking failure of the locking means. 8. The cam angle detection means outputs a cam angle signal for detecting a defect at a different cam angle from the plurality of cam angle signals for cylinder discrimination. 8. The variable valve timing control for an internal combustion engine according to claim 7, wherein at least one of a lock failure and a lock release failure is determined from the magnitude of the variation in the advance amounts of the plurality of cam angle signals including the cam angle signal. apparatus. 9. The lock detection unit determines that the lock release failure is detected when a variation in the advance amount of the plurality of cam angle signals is within a predetermined value in an area where the lock unit needs to be in the unlocked state. The variable valve timing control device for an internal combustion engine according to claim 7 or 8, wherein 10. The failure detecting means determines that a lock failure occurs when a variation in the advance amount of the plurality of cam angle signals is equal to or greater than a predetermined value in an area where the lock means needs to be in a locked state. The variable valve timing control device for an internal combustion engine according to any one of claims 7 to 9, wherein: 11. The defect detection means, wherein the target advance position is separated from the intermediate lock position by a predetermined value or more.
The variable valve timing of an internal combustion engine according to any one of claims 7 to 10, wherein when the time during which the actual advance position is within the predetermined value from the intermediate lock position continues for a predetermined time or more, the lock release is determined to be defective. Control device. 12. An unlock failure recovery control means for applying a hydraulic pressure to the lock means in the unlock direction when the failure detection means detects an unlock failure. The variable valve timing control device for an internal combustion engine according to any one of claims 11 to 11. 13. A valve timing control means for variably controlling a valve timing by changing a rotation phase of a camshaft with respect to a crankshaft of an internal combustion engine (hereinafter referred to as a "camshaft phase") by hydraulic pressure, and while the internal combustion engine is stopped and started. And a lock means biased to lock the camshaft phase at an intermediate lock position located substantially in the middle of the adjustable range of the camshaft phase. A crank angle detecting means for outputting a crank angle signal; a cam angle detecting means for outputting a cam angle signal at a plurality of cam angles; and a variation in advancing amounts of the plurality of cam angle signals with respect to the crank angle signal. Variable valve timing for an internal combustion engine, comprising: unlock detection means for determining whether the lock means is unlocked. Control device. 14. The cam angle detecting means outputs a plurality of cam angle signals for cylinder discrimination and a cam angle signal for unlock detection, and the unlock detection means outputs the cam for unlock detection. 14. The variable valve timing control device for an internal combustion engine according to claim 13, wherein the presence or absence of unlocking of the locking means is determined based on the degree of variation in the advance amount of a plurality of cam angle signals including the angle signal. 15. The lock release detecting means determines that the lock means has been released when the actual advance position of the camshaft phase is separated from the intermediate lock position by a predetermined value or more. Item 15. The variable valve timing control device for an internal combustion engine according to item 13 or 14.